Wireless power transfer (“WPT”) or wireless energy transmission is the transmission of electrical power from a power source to a consuming device without using solid wires or conductors. It is a generic term that refers to a number of different power transmission technologies that use time-varying electromagnetic fields. Wireless transmission is useful to power electrical devices in cases where interconnecting wires are inconvenient, hazardous, or are not possible. In wireless power transfer generally, a transmitter device connected to a power source transmits power by an electromagnetic field across an intervening space to one or more receiver devices, where it is converted back to electric power and utilized.
Wireless power techniques fall into two categories, non-radiative and radiative. In near-field or non-radiative techniques, power may be transferred over short distances by magnetic fields using inductive coupling between coils of wire (also known as inductive power transmission). Typically, in inductive power transmission, the circuit acting as the power source generates an alternating current that is fed to a first set of coils, which responds to the alternating current by producing an alternating magnetic field that permeates the space around it. A second circuit acting as the load, containing a second set of coils, is placed in such a way as to immerse the second set of coils in the magnetic field generated by the first circuit. The second set of coils in the second circuit responds to the alternating magnetic field by generating an electromotive force, EMF, that can in turn generate a current in the second circuit, effectively transferring power form the first circuit to the second circuit. Additional circuitry on the second circuit may rectify the alternating current so that direct current devices can be utilized. If the first circuit, also known as a transmitter, and the second circuit, also known as a receiver, are tuned so that they resonate with each other, greater distances and more efficiency can be achieved.
Applications of this type are electric toothbrush chargers, RFID tags, smartcards, and chargers for implantable medical devices like artificial cardiac pacemakers, and inductive powering or charging of electric vehicles like trains or buses. More recently, wireless systems utilizing inductive power transmission “IPT” (also known as inductive wireless charging) have been developed to charge mobile and handheld computing devices, such as cellphones, digital music players, and portable computers without being tethered to a wall plug. These IPT devices are currently being utilized in the automotive/mass transport industries, as well as in some major restaurant chains, which allows people to leave their cables and chargers at home.
As aircraft interiors continue to integrate electronic devices, as well as become more compatible with personal electronic devices (“PEDs”) brought aboard by passengers, IPT offers an opportunity to operate these PEDs in the aircraft cabin without being encumbered by electrical power lines, as well as a way to provide more robust electrical power supply systems for devices mounted on articulating components. In addition to supplying power for PEDs directly, IPT can be used to provide a station for charging devices that contain batteries, whether they are integrated into the cabin or a passenger's PED.
In particular, IPT offers an attractive alternative to other forms of wireless charging that require the user to either alter the battery pack in the device, or attach an unattractive/obtrusive charging case to charge the device conductively (i.e., to form a metal-to-metal connection between the charger and the device requiring charging). These conductive charging stations are undesirable in aircraft because of the exposure to various elements, such as spilled drinks, foreign debris, etc. In contrast, IPT can be used with a variety of surfaces, profiles, and materials positioned between the charger and the device requiring charging. As a result, IPT is a good candidate for integrating within different components in aircraft seat structures.
A drawback to the adoption of IPT generally has been the lack of a uniform charging standard. Currently, there are three major charging standards that the mobile industry is supporting: Qi, which is supported by the Wireless Charging Consortium (“WPC”), Rezence, which is supported by Alliance for Wireless Power (“A4WP”), and Powermat, which is supported by the Power Matters Alliance (“PMA”). In January 2015, A4WP and PMA announced that the two organizations will merge into a new organization with the intent to consolidate the industry.
Qi is an interface standard developed by the WPC for inductive electrical power transfer over distance of up to 4 cm (1.6 in) based on resonant inductive coupling. It comprises a power transmission pad and a compatible receiver in a portable device. Low-power delivers up to 5 W (typically used to charge mobile devices), medium-power delivers up to 120 W (typically used to power displays and laptops), and high-power will deliver up to 1 kW, allowing powering kitchen utensils, etc.
Some specific drawbacks to adoption of IPT in aircraft, among others, has been the concern over wasting power consumption when no device requiring charging is present, overheating the lithium ion batteries, and over-charging. Recent developments in IPT printed circuit board (“PCB”) technology have addressed many of these concerns by including technology that discerns between metallic objects (such as soda cans, keys, metal heat transfer elements built into aircraft components) and PEDs so that the power transfer is only initiated when a PED is present. Furthermore, the IPT PCB has been provided with the ability to prevent power transfer when the temperature in the PED exceeds a threshold value, such as 60° C. The IPT PCB has also been provided with the ability to detect charging capacity and terminate power transfer when the charging capacity of the PED reaches 98%. With these improvements, IPT technology has recently been approved by the FAA for inclusion in aircraft generally.
Thus, with the recent FAA approval, it is desirable to design aircraft passenger seats that incorporate IPT technology in locations that facilitate wireless charging of PEDs through various modifications of the seat components without negatively impacting manufacturing costs, material costs, and/or installation and use of such seats.